Improve tuplesort.c to support variable merge order. The original coding
Tom Lane <tgl@sss.pgh.pa.us>
Improve tuplesort.c to support variable merge order. The original coding with fixed merge order (fixed number of "tapes") was based on obsolete assumptions, namely that tape drives are expensive. Since our "tapes" are really just a couple of buffers, we can have a lot of them given adequate workspace. This allows reduction of the number of merge passes with consequent savings of I/O during large sorts. Simon Riggs with some rework by Tom Lane
Files
| Path | Change | +/− |
|---|---|---|
| src/backend/optimizer/path/costsize.c | modified | +12 −9 |
| src/backend/utils/sort/tuplesort.c | modified | +154 −53 |
| src/include/utils/tuplesort.h | modified | +3 −1 |